1. Field of the Invention
The present invention relates to composite wheel assemblies for vehicles having an overlay permanently attached to a wheel, and particularly to an improved method and apparatus for permanently attaching an ornamental overlay to the wheel by injecting foam through a nest such that a separate pour opening in the wheel is not required.
2. Description of the Related Art
Decorative overlays are widely used to enhance the aesthetic appearance of automotive wheels. Numerous structural combinations of overlays with chrome-plated outboard surfaces have attracted great interest from vehicle manufacturers, because they are lightweight, aesthetically pleasing and offer designers complete flexibility with regard to the aesthetic effect that can be created for a specific vehicle regardless of whether these vehicles use steel or aluminum wheels.
There are several known methods of adhering a wheel cover to a wheel as will be discussed hereinafter. U.S. Pat. No. 3,915,502 to Connell teaches an annular-shaped wheel cover that is permanently attached to the wheel with double-sided adhesive tape. The adhesive tape is positioned midway between the rim and the center hub area of the wheel, while the remainder of the wheel cover is spaced apart from the outboard surface of the wheel. Connell positions the adhesive tape at radially outward portions of the wheel in order to avoid the deleterious effects of heat generated by the tire, wheel and brake. While some pressure-sensitive adhesive tapes can be effectively used in temperatures up to 500° Fahrenheit (260° C.), the cost of such adhesive tapes is generally prohibitive for use in mass production applications such as securing an overlay to a wheel. Consequently, such applications are generally limited to the use of less expensive adhesive tapes that have relatively low maximum operating temperatures, necessitating that their placement be restricted to the radially outward surfaces of the wheel. Unfortunately, doing so severely limits the adhesive tape's ability to reliably adhere the overlay to the wheel. Further, the adhesive tape's thickness creates a void between the overlay and the wheel that can collect dirt and debris that may affect the balance of the wheel.
To avoid such problems, the prior art proposes the use of a urethane foam adhesive which effectively holds the wheel cover in place, closes the void between the overlay and the wheel, reduces noise, and provides theft deterrence. This method is best described in U.S. Pat. No. 3,669,501 to Derleth that discloses an annular-shaped overlay composed of a thin plastic cover formed from acrylonitrile-butadiene-styrene (ABS) mounted to a wheel spider. The overlay is configured to have variations in contours in a direction transverse to the axis of the wheel that exceed the variations in the rim and/or disc contour of the wheel, which variations would be extremely difficult and expensive, if not impossible, to stamp or draw in the disc of the wheel. During assembly, a foamable polyurethane adhesive is coated on the wheel, and the cover is then quickly clamped to the wheel before the polyurethane begins to foam. As such, the void between the wheel and cover is filled with the polyurethane foam. However, any excess polyurethane foam around the bolt holes or at the periphery of the assembly surrounding the axle hub will squeeze out if appropriate sealing provisions are not made.
One obvious shortcoming of the process disclosed by Derleth is that the composite wheel must be imperforate, except for the small bolt openings necessary for attaching the wheel to a vehicle. It is understood by those skilled in the art that it is necessary to avoid the deleterious effects of heat generated by the wheel and brake, that cause the ABS plastic overlay to distort, cause delamination of any surface treatment, i.e. paint, plating, etc., and further cause the foam adhesive to degrade, distort and eventually melt. Furthermore, wheels assembled according to the Derleth disclosure were very heavy due to the high density of the foam, and variation in localized foam density resulted in severe wheel imbalances.
Turbine openings dissipate heat generated by the brake system and may be configured to provide a variety of distinct aesthetic impressions that add individuality and style to a vehicle. Any opening in the wheel or overlay using the process disclosed in Derleth is a pathway for the foam mixture to escape when it begins to foam and/or cure. Larger openings, such as turbine openings, would not be possible using the Derleth process without additional structure to seal the openings and prevent the foam material from escaping.
It is appreciated by those skilled in the art that it is advantageous to completely fill the cavity with foam adhesive to acoustically dampen any sound produced when the overlay is struck. A drawback of the process according to Derleth is that excess foam mixture is required to ensure that the cavity between the cover and the wheel is completely filled, and subsequently any excess foam must be manually removed, which adds significant cost to the process.
An improved apparatus for attaching a wheel cover to a wheel is taught by U.S. Pat. No. 6,346,159 to Chase, assigned to the assignee hereof. Chase discloses an overlay aligned with, located, and clamped to the wheel with the exception of predetermined sealed areas. The outboard surfaces of the overlay and wheel are spaced apart, leaving a cavity therebetween. Localized nests at strategically placed locations act on the wheel and overlay assembly to seal the assembly on the wheel and thereby create a mold cavity. Net standoffs may be used to assist locating the cover with respect to the wheel and the localized nests interact with the overlay and wheel assembly to create a mold cavity between the overlay and the wheel into which the liquid foam is injected and allowed to react to fill the cavity. A metering unit is used to accurately mix and dispense the two component urethane foam. A nozzle engages a fill port machined into the wheel spider in the back side of the wheel to inject the foamable material in the cladding/wheel assembly cavity.
A disadvantage with the Chase invention is that the wheel must be provided with a fill port through which the urethane foam is injected. Accordingly, the Chase invention requires an additional process of machining the fill port in the wheel spider such that the overall process is more expensive. Furthermore, the additional process for machining the fill port degrades the structural integrity of the wheel by removing material therefrom.
U.S. Pat. No. 5,098,272 to Joseph et al. specifically addresses the aforementioned problem identified with respect to Chase by providing an apparatus for injecting adhesive into the mold through a pre-existing bolt hole in the wheel. Unfortunately, the Joseph et al. invention is limited to applications wherein the wheel cover extends radially beyond the bolt hole circle in the wheel such that adhesive injected into the bolt hole of the wheel is introduced within the mold formed in part by the wheel and the wheel cover. Furthermore, it would be desirable to have the flexibility of injecting the adhesive through locations other than the bolt holes for a variety of reasons including but not limited to the following. First, depending upon the configuration of the mold and the flow characteristics of the particular adhesive, it is often preferable to inject the adhesive into specific regions of the mold to ensure it is completely and uniformly filled, whereby the flexibility of selecting the injection location allows optimization of the injection process for the specific application. Additionally, in some applications the fixturing devices, locating devices, clamping systems, nesting systems and/or injection apparatus may limit accessibility to certain regions of the mold such that it would be desirable to have a variety of potential injection locations from which to choose.
From the above, it can be appreciated that the method and apparatus for attaching a wheel cover to a wheel are not fully optimized. Therefore, what is needed is an economical method and apparatus for assembling an overlay to a wheel by injecting adhesive into a mold through an existing wheel aperture.